ABSTRACT
This report describes the synthesis of a seventeen-membered macrocyclic ring containing ligand (L1) by the reaction of 1,8-bis(2-(chloromethyl)phenoxy)octane with selenium powder. The trans-palladium dichloride complex (C1) of the macrocyclic selenium ligand was synthesized from its reaction with the Pd(CH3CN)2Cl2 precursor. The formation of the ligand and complex was authenticated with the help of various analytical techniques like 1H and 13C{1H} NMR, HRMS, FTIR, UV-visible spectroscopy, and elemental analysis. The structure of the ligand and its coordination mode with the palladium precursor were authenticated with the help of single crystal X-ray diffraction. The complex possesses a distorted square planar geometry around the palladium center. The new ligand and complex are air and moisture insensitive and stable at room temperature for over three months. The variable temperature NMR data and computational studies suggest selenium inversion in the palladium complex (C1) with an inversion barrier of â¼22.6 kcal mol-1. The palladium complex C1 was used as a catalyst for the dehydroxymethylation of long alkyl chain containing dihydroxy compounds. Generally, two separate catalysts are used for dehydroxymethylation (one for the oxidation of the alcohol and the other for the decarbonylation of the aldehyde). Here a single catalyst shows the dual action of dehydroxymethylation with up to 91% yield under only 5.0 mol% catalyst loading. A broad substrate scope can be achieved with good functional group tolerance. The PPh3 and Hg poisoning tests suggest the homogeneous nature of the reaction. Interestingly, the same long alkyl chain containing dihydroxy compounds were reported to undergo macrolactonization when reacted with a ruthenium catalyst.
ABSTRACT
An enzyme-free electrochemical approach for ultra-trace quantification of the organophosphate insecticide malathion is proposed in this study. It is premised on screen-printed carbon electrodes modified by the MIL-88B(Fe) metal-organic framework (MOF). A one-pot solvothermal method was used to synthesise MIL-88B(Fe). The surface modification of electrodes allowed for increased electroactive surface area and accelerated electron transport on the electrode. Inhibition in the redox signal of MIL-88B(Fe) was observed due to the affinity between metal centres of the MOF and the functional groups of malathion, leading to an accurate determination of malathion. The proposed sensor effectively quantified malathion in the wide concentration range of 1 × 10-12 M to 1 × 10-6 M. The limit of detection for malathion was 0.79 pM. The proposed sensor also possessed excellent stability, repeatability, and anti-interference characteristics. Furthermore, the proposed sensor demonstrated satisfactory malathion recovery in spiked vegetable samples.
ABSTRACT
This study presents a novel strategy to fabricate an electrochemical sensor based on a screen-printed electrode (SPE) modified by a bimetallic Mn2+/Fe3+ metal-organic framework (MnFe-MOF) for the direct determination of organophosphate pesticide chlorpyrifos. Square wave voltammetry technique was employed for the electroanalysis, and the limit of detection remained as low as 0.85 nM or 0.29 ppb in a wide linearity range of 1.0 × 10-9 to 1.0 × 10-7 M. The sensor also demonstrated exceptional repeatability and anti-interference performance. Moreover, MnFe-MOF was synthesized using terephthalic acid as the building block using a one-pot solvothermal approach. Multiple characterization studies confirmed the formation of the MOF. The bimetallic MnFe-MOF exhibited high adsorption and electrocatalytic properties towards chlorpyrifos due to the hetero-metal synergism arising between the Mn2+ and Fe3+ ions, owing to which it was employed as the electrode material for non-enzymatic electro-determination of chlorpyrifos. The proposed sensor displayed a satisfactory recovery of the spiked pesticide in real-sample matrices.
